After the invention of the light bulb, lighting devices have become ubiquitous in society. Nearly all private and public buildings and/or spaces have some form of a lighting device to provide some form of general illumination, whether it is to illuminate a room, hallway, street, roadway or the like. The number of lighting devices in the world numbers in the billions.
Since lighting devices are located in most populated areas, the lighting devices have also been used to provide functions besides lighting. For example, lighting devices have incorporated sensors such as room occupancy sensors that are used to control light, smoke detectors and/or gas detectors, such as sensors of carbon monoxide, carbon dioxide, or the like, that are used to alert persons in the vicinity of and/or remote from the lighting device of the presence of smoke and/or a harmful gas. Sensors integrated into lighting devices typically have been single purpose devices. For example, to implement occupancy sensing, smoked detection and carbon dioxide sensing in one lighting device might involve installation of three different types of sensors for the different purposes in one lighting device.
One device that may be used to analyze multiple chemicals simultaneously is a spectrometer. Spectroscopy is a valuable chemical analysis tool. A spectrometer is a device that measures the optical spectrum or wavelength(s) of received light. In particular, the optical power of individual bands within the electromagnetic spectrum including ultraviolet, visible light, and infrared, both the near-infrared (NIR) and thermal infrared, may be measured by a spectrometer. For example, spectrometers measure light reflected from a particular object or passing through the environment (e.g., air) that has been illuminated by a light source having known parameters or characteristics. The spectral output data may be values representing a spectral power distribution of the detected light. The spectral output data may be compared to known spectral values of different compounds, objects or the like to determine characteristics of an object reflected, shifted/retransmitted or passively transmitted by the light from the known light source. Spectrometers typically fall into three wavelength categories: (250-1000 nm) that includes Ultraviolet (U*V), visible, near infrared (NIR) light; (1000-3000 nm) that includes “mid-wave” light; and (3000-18000 nm) which includes thermal infrared. More typical is a filter that detects light in the wavelength range of 3000-5000 nm or 8000-1200 nm. For example, certain bacteria fluoresce when struck, for example, by ultraviolet or infrared light, and one or more wavelengths in the spectral power distribution of the emitted fluorescent light can be used to determine the type of bacterial being illuminated.
While cameras typically use red, green, and blue visible light filters when producing an image, spectrometers have a greater spectral resolution than cameras. A spectrometer detects intensity of a greater number of different wavelengths or wavelength bands than can be distinguished via a camera's few visible light filters. A spectrometer may be made using a larger number of narrowband light wavelength filters over an imaging device. Alternatively, a spectrometer may be made using a prism or a diffraction grating positioned such that the output of the prism is directed to an imaging device. The imaging device is responsive to the various wavelengths of light and outputs a signal representative of the incident intensity of the light of each particular narrow wavelength band. Based on the incident wavelength intensity, a computer processor is able to determine a type or even the chemical composition of an object passing, reflecting or emitting the light in the particular spectral power distribution. Spectrometers may be configured to analyze multiple chemicals simultaneously.
New spectrometer technology is being drastically reduced in price and size. Spectrometers previously cost 10s of thousands of dollars and were large. The smallest of these spectrometers could only fit on top of a desk. However, in recent years, spectrometers have become small enough to fit in a person's hand. Less precise than a spectrometer is a spectral sensor that is able to sample a couple, or a few, wavelengths.
An optical fiber cable is made up of threads of glass or plastic known as optical fibers such that one cable can have as few as two threads or as many as several hundred threads, each of which is capable of transmitting data modulated into light waves. Optical fibers typically include a transparent core having a higher index of refraction surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fiber to act as a waveguide. Some light travels in the cladding as an evanescent wave, which includes all the wavelengths of the light that are outputted by the light source. Some recently developed spectrometers have the capability of receiving signals from optical fiber cables. The cladding material, however, helps limit loss of light from the fiber cable into the region around the cable.
While others have suggested the integration of a spectrometer with a fixture lens, those suggested integrations had limitations not only due to spectrometer size and processing power present at the respective light fixture but also due to limited flexibility in the system. As such, only limited functionality was described or suggested. In addition, updating the capability of a spectrometer previously may have required replacing the spectrometer, which after being collocated with a light fixture presents challenges that were expensive and time consuming.